Current and past methods of atmospheric leaching of primary metal sulfides, like Chalcopyrite, Tennantite, and Enargite suffer from slow reaction kinetics and poor metal dissolution rates and recoveries due, in part, to the formation of polysulfides and of iron-deficient sulfides (Cu1-xFe1-yS2-z) which lead to surface passivation films.
Even with pretreatment by ultra-fine grinding (e.g., P80 of 5-15 μm), surface passivation reactions continue to be problematic. Efforts to reduce leach times to under 5-6 hours in which the concentrates are pretreated, prior to leaching, by ultra-fine grinding of metal sulfides have been unsuccessful. Improved methods are needed to reduce leach times and increase metal recoveries to 98%+ with grinding energies as low as 100-300 kW·h/tonne of copper produced.
Still others have attempted to avoid the surface passivation reactions that plague the leaching of primary sulfides by chemical pre-treatment of chalcopyrite to effect its quantative conversion to a variety of more-readily-leached iron-deficient copper sulfide phases. The success of these various approaches depends upon the degree of conversion of chalcopyrite to covellite, which needs to be as close to 100% as practical. For example, U.S. Pat. No. 6,592,644 (now abandoned) teaches on the quantitative conversion of chalcopyrite (CuFeS2) to covellite (CuS) and pyrite (FeS2) prior to leaching under oxidizing conditions. The conversion process being represented by the following equation:CuFeS2+S▪→CuS+FeS2 
To proceed at commercially viable rates, the reaction must be carried out at elevated temperatures (e.g., 300-500° C.) and/or catalyzed by microwave irradiation. The present invention departs from all prior art methods involving chalcopyrite metathesis in that the effectiveness is, to a large part, independent of the degree of conversion of chalcopyrite.
Others have attempted to avoid surface passivation reactions by an approach wherein the primary sulfides are quantitatively converted to a mixture of more-readily-leached, secondary copper sulfides (i.e., the semiconductors Cu2S, Cu9S5, Cu1.8S, and the electronic conductor CuS). Several of these chemical approaches being represented by the following equations:CuFeS2+3CuSO4+2SO2+4H2O→2Cu2S+FeSO4+4H2SO4 CuS+CuSO4+SO2+2H2O→Cu2S+2H2SO4 
Reactions involving reducing agents, like sulfur dioxide, are inefficient because they involve secondary reactions which convert extensive amounts of already solubilized copper to insoluble copper sulfide. In this approach (For Example U.S. Pat. No. 4,256,553) significant levels of chalcopyrite conversion to secondary sulfides is required to reach acceptable levels of copper recovery during oxidative leaching. The use of a reducing agent represents an additional material handling cost and process complications.
Still other prior art methods have attempted to increase leach rates and copper recoveries through the use of solid-state chemical metathesis of chalcopyrite to a mixture of covellite, chalcocite (Cu2S) and digenite (Cu1.8S) (see for example, G. M. Swinkels and R. M. G. S. Berezowsky, “The Sherritt-Cominco Copper Process—Part 1: The Process,” CIM Bulletin, February 1978, pp. 105-121; see also R. D. Peterson and M. E Wadsworth, “Solid, Solution Reactions in the Hydrothermal Enrichment of Chalcopyrite at Elevated Temperatures,” The Minerals, Metals & Materials Society, EPD Congress, G. Warren Ed., pp. 275-291, 1994; and W. A. Yuill, D. B. Wilson, R. O. Armstrong and B. A. Krebs, “Copper Concentrate Enrichment Process,” presented at the AIME Annual Meeting, Los Angeles, Calif., February 1984). These solid-state reactions involve the replacement of iron within the chalcopyrite lattice by copper. These metathesis reactions are characteristically slow because they involve the solid-state diffusion of copper and iron through the product layer as the rate controlling step. These reactions may take as much as 100 hours to complete. Several of these metathesis approaches are represented by the following equations:CuFeS2+CuSO4→2CuS+FeSO4 CuFeS2+3CuSO4+3FeSO4→2Cu2S+2Fe2(SO4)3 5CuFeS2+11CuSO4+8H2O→8Cu2S+5FeSO4+8H2SO4 5CuS+3CuSO4+4H2O→4Cu2S+4H2SO4 6CuS+3CuSO4+4H2O→5Cu1.8S+4H2SO4 
As with other prior art methods there is a need with these approaches to achieve near-complete conversion of chalcopyrite to the more-readily-leached secondary sulfides. Furthermore, prior art metathesis reaction methods utilize molar ratios of Cu2+/CuFeS2 that are equal to or greater than one (e.g., 1-4). These high molar ratios of Cu2+/CuFeS2 represent an inefficiency in the use of metathesis reactions and raises the difficult issue of economically sourcing sufficient amounts of Cu2+ to carry out the metathesis reactions.
Additionally, metathesis reactions require the use of high temperatures (e.g., 175-200° C.) under autoclave conditions to achieve the required degree of conversion within acceptable process times. Even with the use of high temperatures, accompanied by ultra-fine grinding of the feed, reaction times of 10-100 hours are required to reach 40-90% conversion of chalcopyrite to secondary sulfides. Additionally, several of the approaches involve the production of acid which is problematic as it involves the oxidation of sulfide to sulfate, thereby adding to the cost of the process.
Attempts to carry out chemical metathesis reactions under atmospheric conditions have met with little success (see H-J. Sohn and M. E. Wadsworth, “Chemical Conversion of Chalcopyrite to Copper Sulfides,” SME-AIME Annual Meeting, Los Angeles Calif., February 26-Mar. 1, 1984). Metathesis reactions at lower temperatures, using prior art methods, require pre-grinding of the feed in attritor mills for one hour or longer and reaction conditions of 0.5 wt % solids. These requirements make low-temperature metathesis uneconomical. Furthermore, this approach is also plagued by parasitic side reactions which consume CuSO4 to yield products like Cu1.8S, which are undesirable.
More efficient activation processes for improving the hydrometallurgical processing of primary metal sulfides are needed. Unlike prior art methods wherein the extent of oxidative Cu dissolution is directly proportional to the degree of chemical metathesis, an improved method is needed wherein an activated semiconductor product is produced. The improved method would provide for a chemical reaction which leads to new chemical compounds displaying enhanced reactivities, in much the same way that doping of semiconductors is used to introduce point defects. A purpose for creating such compounds would be to enhance electronic and/or photonic properties. An improved activation process would be: 1) rapid—requiring as little as 1-60 minutes to complete, 2) able to function efficiently at moderate temperatures (e.g., less than 100° C.), able to operate efficiently at high solids concentrations, 3) acid neutral—that is not consume or produce acid, 4) capable of enabling copper dissolution to levels in excess of 90-95% in 3-6 hours or less. Additionally, an improved activation process would be free of parasitic side reactions which consume Cu++ which in turn diminishes the reactivity of the semiconductor product.
A need exists for new chemically reactive compounds which can be readily prepared on a large scale from common copper ores and concentrates containing primary sulfides like chalcopyrite, and from which copper can be easily extracted by oxidative dissolution. The subject matter disclosed herein at least partially satisfies this need.